1. Field of the Invention
The present invention relates to a method for producing an oxide superconductor film.
2. Description of the Related Art
Various types of superconductors such as metallic, ceramic or organic superconductors have been known for a long time. Recently, oxide superconductors having very high critical temperatures (Tc) have attracted much attention. Generally, the oxide superconductor is prepared by drying powdery oxides or carbonates of constituent elements, then repeating press molding, presintering and grinding several times and finally press molding and sintering the ground presintered material. In this method, to produce a homogeneous dense sintered product, troublesome steps must be repeated, and the sintered product has a limited thickness. Therefore, a thin film of superconductor cannot be produced by the sintering method.
To make use of unique properties of the oxide superconductor, many methods have been proposed for producing its thin film. For example, in vacuum deposition, the superconductor forming oxides are heated and evaporated under reduced pressure and deposited.
In the production of the oxide superconductor, a content of oxygen in the superconductor has a great influence on the characteristics of the superconductor. In case of a multicomponent oxide such as the oxide superconductor, when a thin film of an oxide is formed by the vacuum deposition, the composition of the deposited oxide greatly deviates from that of the raw material oxides because the oxides have different vapor pressure from each other. In addition, the oxides may be decomposed into metal elements and elemental oxygen. Therefore, from the obtained superconductor, a part of the oxygen which is required to impart the superconductive properties to the material is eliminated so that the composition of the superconductor suffers from shortage of oxygen. Therefore, the thin film of the superconductor formed by the vacuum deposition has an inhomogeneous composition and cannot have satisfactory superconductive properties.
When the superconductor is used for a power transmitting material, it should be processed in the form of an elongate body. However, it has been impossible to form a practically useful elongate body of superconductor by the conventional method such as the sintering method.